She has purple fur and a pink bow in the middle of her forehead. She is an energetic, selfish, spoiled, sassy troublemaker who sometimes doesn't tell the truth, but remains loyal to her friends. She is a young, sweet beauty. Cleo is the opposite of Matt, that is why they are so attracted to each other. Her catchphrase is: "Have I ever steered you wrong?", which she inadvertently does immediately after saying this. After Cleo says that her friends usually say "well...yeah" and in make-believe games with Clifford and T-Bone, she portrays "the evil Fluffy-Face." She is one of Clifford and T-Bone's best friends.
Voiced by Cree Summer.
Cleo can sometimes prove to be kinda pushy and sensitive. In the episode "Follow the Leader", Cleo wouldn't give up being the leader to Clifford or T-Bone. She sometimes can be hard to handle, but her friends don't mind. In the episode "Friends, Morning, Noon and Night", it is shown Cleo has a lot of stuff including pictures of Mrs. Diller and some pictures of herself as a puppy. Cleo has a tag in Clifford's Really Big Movie. She is one of the pets to have not appeared in Clifford's Puppy Days.
- In "Basketball Stories", she is absent.